The present invention relates to a method of manufacturing friction plates for transmitting torque of a driving member to a driven member.
For example, an automatic transmission for use in vehicles employs a friction device such as a clutch device having a plurality of friction plates axially slidably supported on the driving member, and a plurality of friction plates axially slidably supported on the driven member. The frictional engagement of these friction plates which are sandwiched allows to transmit torque from the driven member to the driving member.
The frictional plate is normally formed in a disc-like shape and made of a metal material. An example of the friction plates is illustrated in FIG. 4 which has frictional side surfaces 30, 30 and free ends 30a, 30a, but welded after forming the usual shape of the disc. In order to increase a frictional efficiency of the friction plates, powdered or particulate frictional materials such as a metal or ceramic are coated on the frictional side surfaces 30, 30 of the friction plates with a bonding agent. The coating of the frictional materials on the frictional side surfaces of the friction plates is laborious and time-consuming task. As a result, a thermal flame spraying of frictional materials is employed to deposite them or the frictional side surfaces.
However, a conventional thermal flame spraying has a drawback that a part of the frictional materials as sprayed on the frictional side surfaces is often peeled off during operation of the friction device because of feebly deposited frictional materials on the frictional side surfaces of the friction plates.